Most of us know that riding fast without earplugs makes you deaf. Scientific evidence shows that 40 percent of professional riders, such as police, paramedics, instructors and racers, have damaged their hearing. It's also likely that the sustained wind roar inside a crash helmet, coupled with poor ventilation, can interfere with your concentration and perception.
You might think that earplugs would get round the problem of hearing damage. But, according to doctors, they don't entirely. Earplugs give some protection but a lot of what you're hearing isn't arriving via your ear canal. It's being transmitted through your skull. Essentially, a helmet is a very noisy device attached very intimately to you head. So part of the potential damage comes from direct vibration of the cochlea.
European researchers are leading a new research project aimed at making the average bike lid quieter, and may even produce a helmet-noise rating system. Part of the project which is supported by Europe's helmet manufacturers, will explore ways to attack the noise at source The problem is that a helmet is about the worst shape for noise, and there's not much you can do about that. A longer, more aerodynamic shape, for instance, would have negative effects in an impact.
Nevertheless, there are some interesting options, which will also extend to screen and fairing design.
None of this will be possible until the research team have devised a repeatable helmet noise test, something that doesn't yet exist. Once it does, we could start seeing helmet-noise labeling.